Grievous is all about your group: if everyone takes damage every second and noone use personal “stuff” to try delete ticks by themselves, you won’t keep them up forever, end of the story.
My yesterday experience (I’m healer):
- NW 12 number 1: 2 wipes between 1st and second boss: group disbanded. Had to rec A LOT.
- NW 12 number 2: 10 random deaths total, key timed. Maybe 1 rec before last boss.
More or less same ilvl and rio for the party, I was always the healer. With grievous it ALL relies on the whole group itself.